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      1 /*
      2  * Shared library add-on to iptables to match
      3  * packets by their type (BROADCAST, UNICAST, MULTICAST).
      4  *
      5  * Michal Ludvig <michal (at) logix.cz>
      6  */
      7 #include <stdio.h>
      8 #include <string.h>
      9 #include <xtables.h>
     10 #include <linux/if_packet.h>
     11 #include <linux/netfilter/xt_pkttype.h>
     12 
     13 enum {
     14 	O_PKTTYPE = 0,
     15 };
     16 
     17 struct pkttypes {
     18 	const char *name;
     19 	unsigned char pkttype;
     20 	unsigned char printhelp;
     21 	const char *help;
     22 };
     23 
     24 static const struct pkttypes supported_types[] = {
     25 	{"unicast", PACKET_HOST, 1, "to us"},
     26 	{"broadcast", PACKET_BROADCAST, 1, "to all"},
     27 	{"multicast", PACKET_MULTICAST, 1, "to group"},
     28 /*
     29 	{"otherhost", PACKET_OTHERHOST, 1, "to someone else"},
     30 	{"outgoing", PACKET_OUTGOING, 1, "outgoing of any type"},
     31 */
     32 	/* aliases */
     33 	{"bcast", PACKET_BROADCAST, 0, NULL},
     34 	{"mcast", PACKET_MULTICAST, 0, NULL},
     35 	{"host", PACKET_HOST, 0, NULL}
     36 };
     37 
     38 static void print_types(void)
     39 {
     40 	unsigned int	i;
     41 
     42 	printf("Valid packet types:\n");
     43 	for (i = 0; i < ARRAY_SIZE(supported_types); ++i)
     44 		if(supported_types[i].printhelp == 1)
     45 			printf("\t%-14s\t\t%s\n", supported_types[i].name, supported_types[i].help);
     46 	printf("\n");
     47 }
     48 
     49 static void pkttype_help(void)
     50 {
     51 	printf(
     52 "pkttype match options:\n"
     53 "[!] --pkt-type packettype    match packet type\n");
     54 	print_types();
     55 }
     56 
     57 static const struct xt_option_entry pkttype_opts[] = {
     58 	{.name = "pkt-type", .id = O_PKTTYPE, .type = XTTYPE_STRING,
     59 	 .flags = XTOPT_MAND | XTOPT_INVERT},
     60 	XTOPT_TABLEEND,
     61 };
     62 
     63 static void parse_pkttype(const char *pkttype, struct xt_pkttype_info *info)
     64 {
     65 	unsigned int	i;
     66 
     67 	for (i = 0; i < ARRAY_SIZE(supported_types); ++i)
     68 		if(strcasecmp(pkttype, supported_types[i].name)==0)
     69 		{
     70 			info->pkttype=supported_types[i].pkttype;
     71 			return;
     72 		}
     73 
     74 	xtables_error(PARAMETER_PROBLEM, "Bad packet type '%s'", pkttype);
     75 }
     76 
     77 static void pkttype_parse(struct xt_option_call *cb)
     78 {
     79 	struct xt_pkttype_info *info = cb->data;
     80 
     81 	xtables_option_parse(cb);
     82 	parse_pkttype(cb->arg, info);
     83 	if (cb->invert)
     84 		info->invert = 1;
     85 }
     86 
     87 static void print_pkttype(const struct xt_pkttype_info *info)
     88 {
     89 	unsigned int	i;
     90 
     91 	for (i = 0; i < ARRAY_SIZE(supported_types); ++i)
     92 		if(supported_types[i].pkttype==info->pkttype)
     93 		{
     94 			printf("%s", supported_types[i].name);
     95 			return;
     96 		}
     97 
     98 	printf("%d", info->pkttype);	/* in case we didn't find an entry in named-packtes */
     99 }
    100 
    101 static void pkttype_print(const void *ip, const struct xt_entry_match *match,
    102                           int numeric)
    103 {
    104 	const struct xt_pkttype_info *info = (const void *)match->data;
    105 
    106 	printf(" PKTTYPE %s= ", info->invert ? "!" : "");
    107 	print_pkttype(info);
    108 }
    109 
    110 static void pkttype_save(const void *ip, const struct xt_entry_match *match)
    111 {
    112 	const struct xt_pkttype_info *info = (const void *)match->data;
    113 
    114 	printf("%s --pkt-type ", info->invert ? " !" : "");
    115 	print_pkttype(info);
    116 }
    117 
    118 static struct xtables_match pkttype_match = {
    119 	.family		= NFPROTO_UNSPEC,
    120 	.name		= "pkttype",
    121 	.version	= XTABLES_VERSION,
    122 	.size		= XT_ALIGN(sizeof(struct xt_pkttype_info)),
    123 	.userspacesize	= XT_ALIGN(sizeof(struct xt_pkttype_info)),
    124 	.help		= pkttype_help,
    125 	.print		= pkttype_print,
    126 	.save		= pkttype_save,
    127 	.x6_parse	= pkttype_parse,
    128 	.x6_options	= pkttype_opts,
    129 };
    130 
    131 void _init(void)
    132 {
    133 	xtables_register_match(&pkttype_match);
    134 }
    135